Even for RPs that doesn't really work, just watch the games, I've seen 100 MPH FBs taken yard if they're thrown over the plate without good movement - batters are just that much quicker than a decade ago - but that also leaves them vulnerable to pitchers who can change speeds.
Velocity is added through a combination of nutrition (especially LA pitchers who often are malnourished at 16) and smoothing mechanics, neither of which involves max effort. Max effort is counterproductive, it makes it hard to disguise an offspeed pitch with that kind of motion and it makes it harder to command a FB. Instead, I think with the advanced film techniques they can teach each kid his optimal, repeatable motion that will maximize velocity without sacrificing command or tipping his pitches.
Anything over 95 with movement, combined with at least one plus secondary pitch (the Phillies seem to focus on the changeup, with the slider the next choice) is good enough. A motion that "disguises" the pitch by throwing out out of the pitcher's body (see Kennedy and his 93-94 FB) is also effective. Being able to throw a 4-seamer with high spin, as well as a 2-seamer with a break away (like a changeup, whereas the slider breaks with the pitch, i.e., RH to the right) is ideal.
Notice when they cut down on illegal substances, it wasn't velocity but spin rate that declined, exposing some pitchers as their ball moved less.
